1. Field of the Invention:
The present invention relates to slide fasteners, and more particularly to a watertight slide fastener.
2. Prior Art
There have been proposed many watertight slide fasteners comprising a pair of opposed waterproof stringer tapes and seal means for protection against water leakage between intermeshing rows of coupling elements mounted by extrusion molding on the respective stringer tapes along their inner longitudinal edges.
A typical example of such known watertight slide fastener stringers is disclosed in U.S. Pat. No. 4,312,102, patented Jan. 26, 1982. The disclosed fastener stringer includes a stringer tape made of synthetic rubber and a series of coupling elements mounted on a longitudinal edge portion of the stringer tape. The stringer tape has a thickened sealing member along the longitudinal edge portion. Each coupling element includes a pair of members one on each side of the tape, and a connector extending through the tape and interconnecting the members, each coupling element member having a reduced neck on the sealing member and a coupling head projecting beyond the sealing member. The coupling heads jointly define a groove extending longitudinally along the sealing member, and the sealing member has a surface facing into the groove. When two such stringers are coupled together, the surfaces of the sealing member are brought together into sealing contact, and the interengaging coupling heads are supported by longitudinal portions of the respective sealing members extending between the necks of two adjacent ones of the coupling elements.
With the slide fastener stringers thus arranged, the surfaces of the sealing member are likely to separate when a severe lateral pulling force is applied to the tapes. Further, when subjected to a severe thrust applied perpendicularly to the plane of the slide fastener, the interengaging coupling heads tend to yield in a direction away from the tape. Under heavier load conditions such as occurs when the stringers are used in a diving suit for deep sea use, working might penetrate through the stringers around the respective connectors due to a great amount of pressure difference between the interior and exterior sides of the slide fastener.